What is the two-phase experimental design consisting of a pre-treatment baseline condition (A) followed by a treatment condition (B)?

• A. ABA Design
• B. AB Design
• C. Reversal Design
• D. Multiple Baseline

Answer: (B)

The AB design uses two phases: a baseline phase (A) where the target behavior is observed without any intervention, followed by a treatment phase (B) where the intervention is introduced and behavior is measured again. The idea is to see whether the treatment changes the behavior from the baseline level, giving evidence that the intervention is having an effect. This differs from reversal designs, which cycle back to the baseline after the treatment (ABAB), and from multiple-baseline designs, which stagger baselines across different targets or settings rather than having just a single baseline followed by one treatment phase.